The best orbit for construction of the station is too dependent on a number of parameters to reach a distinct conclusion. Additional study, particularly of performance penalties will be necessary. b. Degree of Automation - A second construction option is the degree of automation of the construction operations. Total automation with control from the ground does not appear to be a viable choice because of the complexity of the system and the size of the operation. High degree of manual involvement is not acceptable because of the number of personnel which would be required and the highly repetitive nature of the tasks. Automation with orbital control and monitoring can be expected to provide the greatest overall system benefits. With automatic equipment to perform the great number of repetitive construction operations, a minimum number of men can control the operation and provide intelligent decision making capability for off nominal or contingency situations. c. Manufacture-Assemble-Depolyment - The construction approach will include some of each of the options of onsite manufacture, assembly of prefabricated components and deployment of a pre-packaged modules. It is expected that on site manufacturing of structure will predominate because of the advantages of transporting pre-processed bulk materials. The material packing density for raw stock is greater and less sensitive to boost loads. On site manufacturing drives the configuration of the SPS toward a regular geometry with simple repetitive operations. Orbiting manufacture of structure stimulated the concept of a continuous structural truss fabrication machine which was termed a "beam building machine." Figure V-A-5-1 illustrates a concept developed at JSC for an experiment on the Space Shuttle. Appendix V-A-5-3 provides additional information on the approach. Several contractors are working on similar "beam building machines" concepts which provides confidence that the construction approach is sound. d. Locomotion Around the Construction Site - Classically movement in space from one point to another is illustrated as a freeflyer. Assessment of the free-flying mode for construction of the SPS indicates that a mode where the transient vehicle remains attached to the construction base or SPS is a better choice. Table IV.A.4.d-l summarizes the comparison. 6. Construction Concepts Within the guideline of automated construction, the SPS structural configuration has a great influence on the construction concept. Construction approaches for the column/cable and the truss configuration in GEO were evaluated in greater detail than the modular buildup of the truss in LEO.
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